A systematic screening of the depigmenting capacity of a variety of phenolics and catecholics, and their congeners, is under study. These include: phenol, catechol, hydroquinone, p-tertiary butyl catechol, p-tertiary butyl phenol, butylated hydroxyanisole, butylated hydroxytoluene, o-phenyl phenol, p-octyl phenol, and p-nonyl phenol. Laboratory animals being used are black guinea pigs and black mice. The object is to provide a model in vivo system to demonstrate the depigmenting capacity of known and suspect depigmenting chemicals. A variety of lipophilic solvents and emulsion bases are under investigation to establish those most suitable for future screening. Dose response curves are being prepared by varying the concentration of test chemicals, based on molarity. The optimal anatomical sites are being evaluated, with primary attention focused on ears, dorsal area of the body, and nipples. Further work shall include histological and histochemical examination of normal, irritated, and depigmented skin by light and electron microscopy. An elucidation of mechanisms involved in the pathogenesis of chemically-induced leucoderma shall be sought.